The present invention relates to a driving method of a printing apparatus employing a non-stabilized power source.
Among printing apparatuses such as typewriters, for example, the daisy-wheel type typewriter has a number of electric actuators such as a platen drive motor, a carriage drive motor, a ribbon feed motor, a ribbon lift motor, a type-wheel drive motor (type select motor) and a printing hammer solenoid, and these electric actuators are generally connected to a non-stabilized power source. Then, combinations of electric actuators operated in response to printing operation, paper feeding operation, spacing operation and carriage returning operation are different.
Thus, because of employing the non-stabilized power source, the current and the voltage acting on each electric actuator are varied according to the combination of operating a plurality of electric actuators.
For example, such a driving method is adopted that in the printing operation, electric currents are supplied to a drive circuit, the carriage drive motor, the type-wheel drive motor, the printing hammer solenoid and the ribbon feed motor simultaneously or continuously during a very short time, and in the spacing operation, electric currents are supplied only to the drive circuit and the carriage motor.
For one example, assuming that the characteristics of the above-mentioned non-stabilized power source are volt-current characteristics shown in FIG. 4 associated with the embodiment, in the printing operation and in the spacing operation, electric currents flowing through respective electric actuators and the drive circuit are as shown in Table 1.
TABLE 1 ______________________________________ Printing Spacing operation operation ______________________________________ Voltage of non-stabilized 12.4 V 13.8 V power source Drive circuit 0.10 A 0.10 A Carriage drive motor 0.67 A 0.88 A Type-wheel drive motor 0.22 A 0.00 A Hammer solenoid 0.10 A 0.00 A Platen drive motor 0.00 A 0.00 A Ribbon feed motor 0.10 A 0.00 A Total current 1.19 A 0.98 A ______________________________________
In the above-mentioned examples of printing operation and spacing operation, because of employing the non-stabilized power source, the current flowing through the carriage drive motor varies even if the driving method of the carriage drive motor is the same, and in the spacing operation wherein operating loads are few, the current through the carriage drive motor increases remarkably, and therefore expensive elements having large maximum assured currents are required to be used as drive circuit elements of this drive motor, and since the driving voltage of the carriage drive motor also becomes large, the exciting time for stopping the motor is required to be extended, and the printing speed of the printing apparatus is reduced.